In a known manner, a mechanical bearing comprises an outer ring and an inner ring which are centred on the same axis and a cage which is arranged coaxially between the inner ring and the outer ring. This cage is a single-piece tubular part that houses rolling elements, which are maintained in relation to one another in order to prevent them from colliding with each other.
The invention relates more particularly to high-speed mechanical bearings such as the bearings used in the sungear of a planetary gearset. Indeed, at a high rotating speed, the rolling elements housed in the cage undergo a substantial centrifugal force. These centrifugal forces are not equivalent across the entire periphery of the cage and generate high stresses at certain zones of the cage. As such, only certain portions of the cage are particularly solicited by the centrifugal forces. The stresses generated in these portions result however from a global deformation of the cage, which implies poor guiding in rotation of the rolling elements.
In practice, the deformation of the cage linked to the centrifugal forces is limited by using a more resistant material and more substantial sections in the most solicited zones. However, these localised reinforcements increase the mass of the cage and therefore generate more substantial centrifugal forces.
In order to overcome these disadvantages, the cage of certain bearings is replaced by a set of independent inserts which are arranged between each pair of rolling elements of the mechanical bearing. These inserts effectively make it possible to maintain the rolling elements separated and overcome the problem of deformation of the cage due to the centrifugal effects. However, this solution is not suited for high-speed mechanical bearings as the rolling elements are not sufficiently maintained and have, therefore, a random kinematics. More precisely, the rolling elements tend to pivot, at high speed, around an axis of rotation other than their main axis of rotation. This parasite movement of rotation implies a misaligning of the rolling elements which is detrimental to the capacity for guiding in rotation of the mechanical bearing.
Moreover, DE-A-10 2012 202 104 discloses a cage of a mechanical bearing which is carried out in two portioned adapted to be assembled to one another. In this document, the cage is segmented into two portions in order to facilitate the method of manufacture and allow for mass production. Indeed, segmenting the cage into two portions makes it possible to use the injection moulding technique to manufacture the two portions of the cage. As such, in the assembled configuration in the bearing, the two portions of the cage are assembled with each other so well that the forces that are applied on a portion of the cage are transmitted to the other portion and the cage is deformed.
Likewise, JP-A-2013-036510 discloses a cage of a mechanical bearing which is segmented into several portions, which facilitates the manufacture of the cage. The various portions of the cage are placed side by side in an abutting manner in the assembled configuration of the bearing so well that there is a transmission of the forces from one portion to the other and a globalised deformation of the cage.
Finally, JP-A-2009 228 682 discloses a bearing wherein the rolling elements are cylindrical rollers maintained by a cage segmented into two semi-circular portions. The two ends of each segment of the cage are provided with a housing in order to partially receive a roller. In the assembled configuration of the bearing, the two segments of the cage are therefore separated at their ends by two rollers. The rollers inserted between the two segments then transmit the forces from one segment to the other, i.e. the two segments cooperate mechanically with each other. The centrifugal forces that are applied on one segment of the cage are therefore transmitted to the other segment, which results in a globalised deformation of the cage.
It is these disadvantages that the invention intends more particularly to overcome by proposing a mechanical bearing that makes it possible to reduce the deformation of the cage linked to the centrifugal forces at high speed, while still retaining good capacities for guiding in rotation.